Things got a little heated on ESPN's live broadcast of the 2013 NBA Draft last night.

Midway through the second round, news broke that Kevin Garnett waived his no-trade clause, giving the Celtics the green light to forge ahead with a blockbuster trade that would send him and Paul Pierce to the Nets.

During an ESPN interview at the draft, Shelley Smith asked Rivers for his take on the Celtics trade. For the most part, he responded as expected.

Here's where things got interesting:

Rivers, who recently departed Boston for a job with the Clippers in Los Angeles, was asked for his response to Simmons' allegations that he "quit on the Celtics."

(A little background: Simmons is a big Celtics fan who disapproves of the Garnett, Pierce trade in general.)

He lit into Simmons on live television, saying "I would like to call him an idiot but I'm too classy for that," before continuing on to accuse Simmons of not knowing the whole story behind his departure.